Stray gassing of transformer oil in distributed solar photovoltaic (DSPV) systems

Over the last decade, South Africa has witnessed a generous amount in the number of failure rates in distribution solar photovoltaic (DSPV) energy transformers that has been derived from the knowledge deficit of the criterion for designing and an appropriate manner of specifying these transformers. Solar photovoltaic producers have underlined a considerable number of technical performance challenges that have not always been taken into consideration in the course of designing transformers. These challenges consists of harmonics and distortion, resulting in superheating of transformer metallic components, degradation of cellulose insulation, stray gassing of oil, short service life and a significant Total Ownership Cost (TOC) for solar photovoltaic producers.This paper present a case scenario of Dissolve Gas Analysis (DGA) carried out on a DSPV energy transformer following the anomalous stray gassing phenomenon unearthed after oil samples were taken for laboratory analysis during routine tests. The unit under study revealed anomalous gas concentrations of Hydrogen, Methane and Ethane, in which, are associate with corona, sparking and local overheating respectively. The findings highlight that a vague definition of the harmonic current loading in the course of designing transformers for DSPV application can potentially lead to the unit to be operated at a loading beyond specification.